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Andrew Cobb Posted on Apr 08, 2016
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I have 1994 chevy 1500 it failed smog at idle . the hc ppm was100 max and i was putting out 848 what should i do. the high idle test at passed fine max is1.0 and i was.95

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Stephen

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  • Cars & Trucks Master 21,873 Answers
  • Posted on Apr 08, 2016
 Stephen
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May not be much you can do yourself without a scanner and an exhaust gas analyzer.
High HC is too much fuel. So it could be a leaking injector, O2 sensor, air flow problem, or something else.
It could also be not up to normal operating temp due to an open thermostat.
Without the proper equipment you really have no way of knowing whats coming out the tailpipe.

5 Related Answers

Anonymous

  • 158 Answers
  • Posted on Apr 05, 2011

SOURCE: My 1997 Honda Civic failed

Jose, I don't know if this will give you the answer you are looking for because there are many things to consider here. The exhaust gas recirculation valve (EGR) is one of the main things involved in reducing NO emissions. This valve is controled by the power control module. (PCM) This is your vehicles computer. The PCM monitors the vehicles speed and will command the EGR to open when the vehicle attains a certain speed, which is why the ASM test being done is recorded at two different speeds. At 25 MPH your vehicle failed the hydrocarbon (HC) emissions limit and this could be for a number of reasons. When is the last time you car was tuned up? Old spark plugs, wires, clogged air filters, oxygen sensors, leaking injectors (personal experience) or the PCV valve could be contributing to the results of the test. I guess that the easiest way to go is to tune up the engine replacing the spark plugs, wires, air filter and the PCV valve and don't forget to have the oil changed at the same time. Only then should have the vehicle retested and see what the results are. Should it fail again you may have to consider having the EGR or the catalytic converter replaced depending on what portion of the test fails. If the NO fails I would consider the EGR. If the HC fails then I would consider the catalytic converter. Good luck with this.

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Anonymous

  • 674 Answers
  • Posted on Nov 24, 2008

SOURCE: ASM 2525 NO ppm TAILPIPE EMISSIONS failure

have you had the the engine codes pulled and reset?
and if so what are your engine codes?
i dont know of any car that will pass emissions test with the engine light on.
we cure your trouble that caused your engine light to come on and you will pass your test.
later
paul

Anonymous

  • 834 Answers
  • Posted on Jul 10, 2010

SOURCE: failed smog check

How well does the vehicle run?

Assuming that the engine did pass the EGR function test on the emission test results, and the MIL (Malfunction Indicator Light) or check engine light is not on when the engine is running, and if you are not sure when the last time it was that the engine had a complete tune-up, with distributor cap, ignition rotor, spark plugs, spark plug wires, air and fuel filters, then a complete tune-up would certainly help, and if the engine oil and oil filter have not been changed in a while, then they should also be changed before an emission test because long used engine oil traps carbon and it will show up as higher CO on the emission test because the emission analyzer will be able detect the higher CO from the engine oil through the PCV valve.

However, it would seem from those HC readings that there is a vacuum leak, and carefully inspect all of the vacuum lines for any cracks or damage, (especially the vacuum line to the fuel pressure regulator) because cracks in the vacuum lines seem to like to hide underneath the lines.

The emission label under the hood should have the vacuum line routing diagram printed on it, and the vacuum lines should all be checked to be certain that they are all connected correctly.

Here is the firing order diagram for that vehicle to help assist you tune-up the vehicle.


e696e87.jpg

Anonymous

  • 1702 Answers
  • Posted on Feb 24, 2011

SOURCE: My 1990 chevy astro van

the smog test looks like the engine is miss firing, that could cause the timing to be out of whack also, try a old fashioned tune up, new spark plugs, wires, and filters also replace the PCV valve. any time you see the NO that high suspect a miss fire.

redds55

Ricky Peters

  • 2620 Answers
  • Posted on May 12, 2011

SOURCE: vehicle inspection, pass primary emissions

First either replace or clean the idle air control valve.You can clean it with a non-chlronated brake cleaner and wire brush.Then take the mass air flow sensor off and do the same but don't use a brush just the cleaner only.

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Related Questions:

0helpful
1answer

I have 1994 chevy 1500 it failed smog at idle . the hc ppm was100 max and i was putting out 848 what should i do

Diagnose a running rich condition. Too much gas, or too little air. Start with a clean air filter. Have your fuel injectors checked for leaking, stuck open, being out of whack. Make sure PCV system is working, along with the EGR. Is ignition system in good shape, good plugs, plug wires, and coil? If ignition is not up to par, you could have unburned gas getting through engine. Remember, it is running too rich. Good luck.
0helpful
2answers

I have a 1994 chevy silverado c1500 v/6 4.3 litre and failed smog for high hc levels st idle . what should i do before i take it back to try and smog? ive already done complete tune up.

as long as you have no check engine light on change oil, air filter. pep boys sells a product called guaranteed to pass add to fuel make sure car is hot when you go back for emission test cold car has high hc levels it also helps to post the hc level you tested at and the limit on your receipt hope this helps
0helpful
1answer
0helpful
1answer

Fail smog test

fist i would like you to post the year make and model of the truck along with the HC ppms and NOX ppm it would be very helpful but high hc and nox can be attributed to a faulty EGR system nox is produced when the combustion chamber temperature gets too high so a small amount of exhaust is cycled back into the air stream to help cool them there are other causes but without looking at the levels its much harder to say
1helpful
1answer

My 1990 chevy astro van didn't pass smog. Paperwork says it failed the following; Ignition timing: 99 ATDC. Also, ASM Emission Test Results; 15mph HC (PPM) max is 122 measured 127, 25mph max is 102...

the smog test looks like the engine is miss firing, that could cause the timing to be out of whack also, try a old fashioned tune up, new spark plugs, wires, and filters also replace the PCV valve. any time you see the NO that high suspect a miss fire.
2helpful
2answers

Need 92 toyota paseo to pass CA smog test ! What causes too high HC in smog test????

High HC means moisture in the system. Try driving it longer then take it to the smog shop. Otherwise it could be hard like a head gasket or easy such as a PCV not functioning. Any ways you should always drive it about 20 miles before smog check, longer when the weather is cold.
1helpful
1answer

Failed smog check

How well does the vehicle run?

Assuming that the engine did pass the EGR function test on the emission test results, and the MIL (Malfunction Indicator Light) or check engine light is not on when the engine is running, and if you are not sure when the last time it was that the engine had a complete tune-up, with distributor cap, ignition rotor, spark plugs, spark plug wires, air and fuel filters, then a complete tune-up would certainly help, and if the engine oil and oil filter have not been changed in a while, then they should also be changed before an emission test because long used engine oil traps carbon and it will show up as higher CO on the emission test because the emission analyzer will be able detect the higher CO from the engine oil through the PCV valve.

However, it would seem from those HC readings that there is a vacuum leak, and carefully inspect all of the vacuum lines for any cracks or damage, (especially the vacuum line to the fuel pressure regulator) because cracks in the vacuum lines seem to like to hide underneath the lines.

The emission label under the hood should have the vacuum line routing diagram printed on it, and the vacuum lines should all be checked to be certain that they are all connected correctly.

Here is the firing order diagram for that vehicle to help assist you tune-up the vehicle.


e696e87.jpg
0helpful
1answer

I have a 1991 chevy pick up with a 5.7l it failed the test 2

You did not post the odometer reading on the van but base on the year it should has over 85,000+ miles on it.

The most likely source of the high Hydrocarbon (HC) is clogged or drippy injectors.

Change the fuel filter if it is over 48K miles.

Ran two or more tanks full of Chevron gas will help clean out the fuel system.

====

The air fuel ratio can be off is the air filter is clogged or the mass air flow sensor give incorrect data to the computer (ECU).

Change the air filter is it over 20,000 miles or you can see sunlight though it.

Use CRC Mass Air Flow cleaner or electronic part clean to gently clean the mass air flow sensor.

==========

Change the oil to 20W50 or one grade higher to prevent blow by.

You current motor oil is soak with HC from blow by.

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Make sure the tires are at 32 psi

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Do the smog test is a COLD morning?

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REMOVE excess cargo off the van.

=======

These are little things that I would do.

If the HC is still high at 25 mph then you will need a professional fuel injector cleaning or replace the injectors.


Please post more data on the third smog test on the comment window.
1helpful
3answers

ASM 2525 NO ppm TAILPIPE EMISSIONS failure

have you had the the engine codes pulled and reset?
and if so what are your engine codes?
i dont know of any car that will pass emissions test with the engine light on.
we cure your trouble that caused your engine light to come on and you will pass your test.
later
paul
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